Single phase fluid imprint lithography method

ABSTRACT

The present invention is directed toward a method for reducing pattern distortions in imprinting layers by reducing gas pockets present in a layer of viscous liquid deposited on a substrate. To that end, the method includes varying a transport of the gases disposed proximate to the viscous liquid. Specifically, the atmosphere proximate to the substrate wherein a pattern is to be recorded is saturated with gases that are either highly soluble, highly diffusive, or both with respect to either the viscous liquid, the substrate, the template, or a combination thereof. Additionally, or in lieu of saturating the atmosphere, the pressure of the atmosphere may be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 10/898,034 filed on Jul. 23, 2004 entitled “Methodfor Creating a Turbulent Flow of Fluid Between a Mold and a Substrate”(now U.S. Pat. No. 7,531,025) which is a divisional of U.S. applicationSer. No. 10/677,639 now U.S. Pat. No. 7,090,716 filed on Oct. 2, 2003entitled “Single Phase Fluid Imprint Lithography Method,” all of whichare incorporated by reference herein.

BACKGROUND

The field of invention relates generally to imprint lithography. Moreparticularly, the present invention is directed to a system forcontrolling a flow of a substance over an imprinting material.

Micro-fabrication involves the fabrication of very small structures,e.g., having features on the order of micro-meters or smaller. One areain which micro-fabrication has had a sizeable impact is in theprocessing of integrated circuits. As the semiconductor processingindustry continues to strive for larger production yields whileincreasing the circuits per unit area formed on a substrate,micro-fabrication becomes increasingly important. Micro-fabricationprovides greater process control while allowing increased reduction ofthe minimum feature dimension of the structures formed. Other areas ofdevelopment in which micro-fabrication has been employed includebiotechnology, optical technology, mechanical systems and the like.

An exemplary micro-fabrication technique is shown in U.S. Pat. No.6,334,960 to Willson et al. Willson et al. disclose a method of forminga relief image in a structure. The method includes providing a substratehaving a transfer layer. The transfer layer is covered with apolymerizable fluid composition. A mold makes mechanical contact withthe polymerizable fluid. The mold includes a relief structure, and thepolymerizable fluid composition fills the relief structure. Thepolymerizable fluid composition is then subjected to conditions tosolidify and polymerize the same, forming a solidified polymericmaterial on the transfer layer that contains a relief structurecomplimentary to that of the mold. The mold is then separated from thesolid polymeric material such that a replica of the relief structure inthe mold is formed in the solidified polymeric material. The transferlayer and the solidified polymeric material are subjected to anenvironment to selectively etch the transfer layer relative to thesolidified polymeric material such that a relief image is formed in thetransfer layer. The time required and the minimum feature dimensionprovided by this technique is dependent upon, inter alia, thecomposition of the polymerizable material.

U.S. Pat. No. 5,772,905 to Chou discloses a lithographic method andapparatus for creating ultra-fine (sub-25 nm) patterns in a thin filmcoated on a substrate in which a mold having at least one protrudingfeature is pressed into a thin film carried on a substrate. Theprotruding feature in the mold creates a recess of the thin film. Themold is removed from the film. The thin film then is processed such thatthe thin film in the recess is removed, exposing the underlyingsubstrate. Thus, patterns in the mold are replaced in the thin film,completing the lithography. The patterns in the thin film will be, insubsequent processes, reproduced in the substrate or in another materialwhich is added onto the substrate.

Yet another imprint lithography technique is disclosed by Chou et al. inUltrafast and Direct Imprint of Nanostructures in Silicon, Nature, Col.417, pp. 835-837, June 2002, which is referred to as a laser assisteddirect imprinting (LADI) process. In this process, a region of asubstrate is made flowable, e.g., liquefied, by heating the region withthe laser. After the region has reached a desired viscosity, a mold,having a pattern thereon, is placed in contact with the region. Theflowable region conforms to the profile of the pattern and is thencooled, solidifying the pattern into the substrate. A concern with thistechnique involves pattern distortions attributable to the presence ofgases in the flowable region.

It is desired, therefore, to provide a system to reduce distortions inpatterns formed using imprint lithographic techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a lithographic system in accordance withthe present invention;

FIG. 2 is a simplified elevation view of a lithographic system shown inFIG. 1;

FIG. 3 is a simplified representation of material from which animprinting layer, shown in FIG. 2, is comprised before being polymerizedand cross-linked;

FIG. 4 is a simplified representation of cross-linked polymer materialinto which the material shown in FIG. 3 is transformed after beingsubjected to radiation;

FIG. 5 is a simplified elevation view of a mold spaced-apart from theimprinting layer, shown in FIG. 1, after patterning of the imprintinglayer;

FIG. 6 is a simplified elevation view of an additional imprinting layerpositioned atop the substrate shown in FIG. 5 after the pattern in thefirst imprinting layer is transferred therein;

FIG. 7 is a detailed perspective view of a print head shown in FIG. 1;

FIG. 8 is a cross-sectional view of a chucking system in accordance withthe present invention;

FIG. 9 is detailed cross-sectional view of an imprint head shown in FIG.7; and

FIG. 10 is a bottom-up perspective view of the imprint head shown inFIG. 9.

DETAILED DESCRIPTION

FIG. 1 depicts a lithographic system 10 in accordance with oneembodiment of the present invention that includes a pair of spaced-apartbridge supports 12 having a bridge 14 and a stage support 16 extendingtherebetween. Bridge 14 and stage support 16 are spaced-apart. Coupledto bridge 14 is an imprint head 18, which extends from bridge 14 towardstage support 16 and provides movement along the Z-axis. Disposed uponstage support 16 to face imprint head 18 is a motion stage 20. Motionstage 20 is configured to move with respect to stage support 16 along X-and Y-axes. It should be understood that imprint head 18 may providemovement along the X- and Y-axes, as well as in the Z-axis, and motionstage 20 may provide movement in the Z-axis, as well as in the X and Yaxes. An exemplary motion stage device is disclosed in U.S. Pat. No.6,900,881, filed Jul. 11, 2002, entitled “Step and Repeat ImprintLithography Systems,” assigned to the assignee of the present invention,and which is incorporated by reference herein in its entirety. Aradiation source 22 is coupled to lithographic system 10 to impingeactinic radiation upon motion stage 20. As shown, radiation source 22 iscoupled to bridge 14 and includes a power generator 23 connected toradiation source 22. Operation of lithographic system 10 is typicallycontrolled by a processor 25 that is in data communication therewith.

Referring to both FIGS. 1 and 2, connected to imprint head 18 is atemplate 26 having a mold 28 thereon. Mold 28 includes a plurality offeatures defined by a plurality of spaced-apart recessions 28 a andprotrusions 28 b. The plurality of features defines an original patternthat is to be transferred into a substrate 30 positioned on motion stage20. To that end, imprint head 18 and/or motion stage 20 may vary adistance “d” between mold 28 and substrate 30. In this manner, thefeatures on mold 28 may be imprinted into a flowable region of substrate30, discussed more fully below. Radiation source 22 is located so thatmold 28 is positioned between radiation source 22 and substrate 30. As aresult, mold 28 is fabricated from a material that allows it to besubstantially transparent to the radiation produced by radiation source22.

Referring to both FIGS. 2 and 3, a flowable region, such as animprinting layer 34, is disposed on a portion of a surface 32 thatpresents a substantially planar profile. A flowable region may be formedusing any known technique, such as a hot embossing process disclosed inU.S. Pat. No. 5,772,905, which is incorporated by reference in itsentirety herein, or a laser assisted direct imprinting (LADI) process ofthe type described by Chou et al. in Ultrafast and Direct Imprint ofNanostructures in Silicon, Nature, Col. 417, pp. 835-837, June 2002. Inthe present embodiment, however, a flowable region consists ofimprinting layer 34 being deposited as a plurality of spaced-apartdiscrete droplets 36 of a material 36 a on substrate 30, discussed morefully below. An exemplary system for depositing droplets 36 is disclosedin U.S. Pat. No. 6,926,929, filed Jul. 9, 2002, entitled “System andMethod for Dispensing Liquids,” assigned to the assignee of the presentinvention, and which is incorporated by reference herein in itsentirety. Imprinting layer 34 is formed from material 36 a that may beselectively polymerized and cross-linked to record the original patterntherein, defining a recorded pattern. An exemplary composition formaterial 36 a is disclosed in U.S. Pat. No. 7,157,036, filed Jun. 16,2003, and entitled “Method to Reduce Adhesion Between a ConformableRegion and a Pattern of a Mold,” which is incorporated by reference inits entirety herein. Material 36 a is shown in FIG. 4 as beingcross-linked at points 36 b, forming a cross-linked polymer material 36c.

Referring to FIGS. 2, 3 and 5, the pattern recorded in imprinting layer34 is produced, in part, by mechanical contact with mold 28. To thatend, distance “d” is reduced to allow droplets 36 to come intomechanical contact with mold 28, spreading droplets 36 so as to formimprinting layer 34 with a contiguous formation of material 36 a oversurface 32. In one embodiment, distance “d” is reduced to allowsub-portions 34 a of imprinting layer 34 to ingress into and fillrecessions 28 a.

To facilitate filling of recessions 28 a, material 36 a is provided withthe requisite properties to completely fill recessions 28 a, whilecovering surface 32 with a contiguous formation of material 36 a. In thepresent embodiment, sub-portions 34 b of imprinting layer 34 insuperimposition with protrusions 28 b remain after the desired, usuallyminimum, distance “d” has been reached, leaving sub-portions 34 a with athickness t₁, and sub-portions 34 b with a thickness, t₂. Thicknesses“t₁” and “t₂” may be any thickness desired, dependent upon theapplication. Typically, t₁ is selected so as to be no greater than twicethe width u of sub-portions 34 a, i.e., t₁≦2u, shown more clearly inFIG. 5.

Referring to FIGS. 2, 3 and 4, after a desired distance “d” has beenreached, radiation source 22 produces actinic radiation that polymerizesand cross-links material 36 a, forming cross-linked polymer material 36c. As a result, the composition of imprinting layer 34 transforms frommaterial 36 a to cross-linked polymer material 36 c, which is a solid.Specifically, cross-linked polymer material 36 c is solidified toprovide side 34 c of imprinting layer 34 with a shape conforming to ashape of a surface 28 c of mold 28, shown more clearly in FIG. 5. Afterimprinting layer 34 is transformed to consist of cross-linked polymermaterial 36 c, shown in FIG. 4, imprint head 18, shown in FIG. 2, ismoved to increase distance “d” so that mold 28 and imprinting layer 34are spaced-apart.

Referring to FIG. 5, additional processing may be employed to completethe patterning of substrate 30. For example, substrate 30 and imprintinglayer 34 may be etched to transfer the pattern of imprinting layer 34into substrate 30, providing a patterned surface 32 a, shown in FIG. 6.To facilitate etching, the material from which imprinting layer 34 isformed may be varied to define a relative etch rate with respect tosubstrate 30, as desired. The relative etch rate of imprinting layer 34to substrate 30 may be in a range of about 1.5:1 to about 100:1.

Alternatively, or in addition to, imprinting layer 34 may be providedwith an etch differential with respect to photo-resist material (notshown) selectively disposed thereon. The photo-resist material (notshown) may be provided to further pattern imprinting layer 34, usingknown techniques. Any etch process may be employed, dependent upon theetch rate desired and the underlying constituents that form substrate 30and imprinting layer 34. Exemplary etch processes may include plasmaetching, reactive ion etching, chemical wet etching and the like.

Referring to FIGS. 7 and 8, template 26, upon which mold 28 is present,is coupled to an imprint head housing 18 a via a chucking system 40 thatincludes a chuck body 42. Chuck body 42 is adapted to retain template 26upon which mold 28 is attached employing vacuum techniques. To that end,chuck body 42 includes one or more recesses 42 a that are in fluidcommunication with a pressure control system, such as a fluid supplysystem 70. Fluid supply system 70 may include one or more pumps toprovide both positive and negative pressure, as well as a supply offluid to facilitate reducing, if not preventing, trapping of gases, suchas air, in imprinting layer 34, shown in FIG. 5. An exemplary chuckingsystem is disclosed in U.S. Pat. No. 7,019,819, entitled “ChuckingSystem For Modulating Shapes of Substrates,” assigned to the assignee ofthe present invention, and which is incorporated by reference in itsentirety herein.

As discussed above, during imprinting template 26 and, therefore, mold28, is brought into proximity with substrate 30 before patterningimprinting material 36 a, shown in FIG. 3, is disposed on a region 77 ofsubstrate 30. Specifically, template 26 is brought within microns ofsubstrate 30, e.g., 15 microns more or less. It has been found desirableto perform localized control of the atmosphere 78 that is proximate toboth template 26 and region 77. For example, to avoid the deleteriouseffects of gases present in imprinting material 36 a, shown in FIG. 3,and/or subsequently trapped in the patterned imprinting layer 34, shownin FIG. 2, it has been found beneficial to control the consistency offluid in atmosphere 78 and/or the pressure of atmosphere 78.

Referring to FIG. 9, to facilitate control of atmosphere 78, chuck body42 is designed to facilitate the passage of fluids proximate to mold 28and imprint head 18 includes a baffle 100 surrounding template 26.Specifically, baffle 100 extends from imprint head 18, terminating in anadir 102 that lies in a plane in which a surface 26 a lies. In thisfashion, mold 28 extends beyond nadir 102 to facilitate contact withregion 77. Chuck body 42 includes one or more throughways, two of whichare shown as 104 and 106. Apertures 104 a and 106 a of throughways 104and 106, respectively, are disposed in a surface of chuck body 42disposed between template 26 and baffle 100, referred to as a peripheralsurface 100 a. Throughways 104 and 106 place apertures 104 a and 106 ain fluid communication with fluid supply system 70, shown in FIG. 8.Baffle 100 functions to slow the movement of fluid exiting apertures 104a and 106 a away from mold 28. To that end, baffle 100 includes firstand second opposed surfaces 102 a and 102 b. First opposed surface 102 aextends from nadir 102 away from substrate 30 and faces template 26.Second opposed surface 102 b extends from nadir 102 away from substrate30 and faces away from mold 28. Although it is not necessary, firstopposed surface 102 a is shown extending obliquely with respect tosecond opposing surface 102 b. With this configuration, atmosphere 78may be controlled by introduction or evacuation of fluid throughapertures 104 a and 106 a. However, first and second opposed surfaces102 a and 102 b may extend parallel to one another from nadir 102.

Referring to FIGS. 3, 8 and 9, in one embodiment, atmosphere 78 isestablished so that the transport of the gases present therein to eitherimprinting material 36 a in region 77, substrate 31, template 26, mold28, or a combination thereof is increased. The term transport is definedto mean any mechanism by which the propagation of gases through eitherimprinting material 36 a, substrate 31, template 26, mold 28, or acombination thereof is increased, e.g., increased solubility, increaseddiffusion and the like. To that end, fluid supply system 70 may includea supply of imprinting material 36 a. Under control of processor 25,which is in data communication with fluid supply system 70, imprintingmaterial 36 a may be introduced through apertures 104 a and 106 a tosaturate atmosphere 78 with imprinting material 36 a. This was found toreduce, if not completely do away with, the quantity of gases, such asair, trapped in the imprinting layer 34, shown in FIG. 5, during imprintprocesses. This is beneficial as it was found that the presence of airin imprinting layer 34, shown in FIG. 5, creates undesirable voids.Alternatively, it was found that by saturating atmosphere 78 with carbondioxide and/or helium the quantity of air trapped in imprinting layer34, shown in FIG. 5, was substantially reduced if not avoided. It shouldbe understood that a mixture of imprinting material 36 a, carbon dioxideand/or helium may be introduced into atmosphere 78 to reduce thequantity of air trapped in imprinting layer 34, shown in FIG. 5.

Referring to FIGS. 2, 9 and 10, a difficulty encountered with respect tointroducing fluids was to ensure that the molecules in the fluid streams104 b and 106 b exiting apertures 104 a and 106 a, respectively,traveled to a region of the atmosphere positioned between mold 28 anddroplets 36, and before contact of droplets 36 with mold 28. This regionof atmosphere 78 is referred to as a processing region 78 a. As shown,apertures 104 a and 106 a are disposed about peripheral surface 100 a,which is spaced-apart from processing region 78 a. Given that theseparation of mold 28 from region 77 is on the order of microns, therelative dimensions of the molecules in fluid streams 104 b and 106 band the spacing between mold 28 and region 77 makes difficult theingression of the aforementioned molecules into processing region 78 a.

Referring to FIGS. 8 and 9, one manner in which to overcome theaforementioned difficulty is to have fluid supply system 70 undercontrol of processor 25. A memory (not shown) is in data communicationwith processor 25. The memory (not shown) comprises a computer-readablemedium having a computer-readable program embodied therein. Thecomputer-readable program includes instructions to pulse fluid streams104 b and 106 b into atmosphere 78 having a desired mixture ofmolecules, discussed above. In this manner, laminar flow of fluidstreams 104 b and 106 b may be avoided. It is believed that by providingfluid streams 104 b and 106 b with turbulent flow, the probability willbe increased that a sufficient quantity of the molecules containedtherein will reach processing region 78 a to reduce, if not avoid, thepresence of gases being trapped in imprinting layer 34. To that end,fluid may be pulsed through both apertures 104 a and 106 a,concurrently, or sequentially pulsed through the same, i.e., first fluidis introduced through aperture 104 a and subsequently through aperture106 a and then again through 104 a, with the process being repeated fora desired time or during the entire imprinting process. Furthermore, thetiming of the flow of gas into processing region 78 a is importantbecause it is desired that a sufficient quantity of molecules containedtherein reach processing region 78 a before contact is made between mold28 and droplets 36.

Referring to FIG. 9, alternatively, fluid may be pulsed through one ofthe apertures, e.g., aperture 104 a, and then evacuated through theremaining aperture, e.g., aperture 106 a. In this manner, fluid would bedrawn across processing region 78 a. It may also be advantageous topulse the fluid through both apertures 104 a and 106 a, concurrently,then evacuate through both apertures 104 a and 106 a concurrently. It isdesired, however, that the flow rate of fluid be established tominimize, if not avoid, movement of droplets 36, shown in FIG. 2.

To ensure that the fluids exiting apertures 104 a and 106 a crossesthrough processing region 78 a, it may be advantageous to concurrentlypulse fluid through both apertures 104 a and 106 a concurrently and thenalternatingly evacuate through one of apertures 104 a or 106 a.Concurrently introducing the fluid through both apertures 104 a and 106a minimizes the time required to saturate atmosphere 78. Alternatinglyevacuating the fluid through one of apertures 104 a and 106 a ensuresthat the fluid travels through processing region 78 a. For example, afirst step would include introducing fluid into atmosphere 78 throughboth apertures 104 a and 106 a. A second step would include evacuatingthe fluid through one of apertures 104 a and 106 a, e.g., aperture 104a. Thereafter, at a third step, fluid would be introduced intoatmosphere 78 through both apertures 104 a and 106 a, concurrently. At afourth step, fluid would be evacuated through one of apertures 104 a and106 a that was not employed in the previous step to remove fluid, e.g.,aperture 106 a. It should be understood that evacuation may occurthrough one of apertures 104 a and 106 a, while fluid is beingintroduced through the remaining aperture of apertures 104 a and 106 a.Alternatively, evacuation may occur in the absence of a fluid flow intoatmosphere 78. The desired result is that fluid ingression intoatmosphere 78 and fluid evacuation therefrom occurs so that the desiredconcentration of fluid is present.

Referring to FIGS. 9 and 10, in another embodiment, a plurality ofapertures may be disposed about peripheral surface 100 a so that each ofthe apertures of a pair is disposed opposite one another on oppositesides of template 26. This is shown by aperture pair 104 a and 106 abeing disposed opposite one another on opposite sides of template 26. Asecond aperture pair is shown as 108 a and 110 a. Apertures 108 a and110 a are disposed opposite one another on opposite sides of template26.

As shown, each of apertures 104 a, 106 a, 108 a and 110 a, are arrangedto lie on a common circle with adjacent apertures being spaced-aparttherefrom by 90°. In this manner, each of apertures 104 a, 106 a, 108 aand 110 a are arranged to facilitate fluid flow in/out of a differentquadrant of chuck body 42. Specifically, aperture 104 a facilitatesfluid flow in/out of quadrant I; aperture 106 a facilitates fluid flowin/out of quadrant II; aperture 108 a facilitates fluid flow in/out ofquadrant III; and aperture 110 a facilitates fluid flow in/out ofquadrant IV. However, any number of apertures may be employed, e.g.,more than one per quadrant with differing quadrants having differingnumbers of apertures and arranged in any spatial arrangement desired.Each of these arrangements should facilitate introduction and/orevacuation of a plurality of flows of fluid streams into atmosphere 78,with a subset of the plurality of flows being introduced to differingregions about template 26. It is believed that introduction of themultiple flows of fluid streams provides a turbulent flow of fluid inatmosphere 78. This, it is believed, increases the probability thatmolecules in the fluid streams would reach processing region 78 a.However, fluid flow into atmosphere 78 through each of the apertures 104a, 106 a, 108 a and 110 a and evacuation of fluid from atmosphere 78therethrough may occur in any manner discussed above.

In another embodiment, a fluid stream may be introduced through each ofapertures 104 a, 106 a, 108 a and 110 a sequentially so that a flow cell112 may be created between template 26 and region 77. Flow cell 112would facilitate ingression of molecules in the fluid streams intoprocessing region 78 a to provide the benefits mentioned above. Forexample, first a fluid flow may be introduced through aperture 104 a andthen terminated. After termination of fluid flow through aperture 104 a,fluid flow through aperture 106 a is commenced to introduce fluid intoatmosphere 78. Subsequently, fluid flow through aperture 106 a isterminated. After termination of fluid flow through aperture 106 a,fluid flow through aperture 108 a is commenced to introduce fluid intoatmosphere 78. Fluid flow in through aperture 108 a is subsequentlyterminated. After termination of fluid flow through aperture 108 a,fluid flow through aperture 110 a is commenced to introduce fluid intoatmosphere 78. In this manner, fluid is introduced into atmosphere 78through a single quadrant at any given time. However, it may bedesirable to introduce fluid into more than one quadrant. Although thismay frustrate creation of flow cell 112, it is within confines of thepresent invention.

Alternatively, sequential introduction and evacuation through apertures104 a, 106 a, 108 a and 110 a may be undertaken to create flow cell 112.This would include introducing fluid through one or more of apertures104 a, 106 a, 108 a and 110 a, concurrently. Subsequently, sequentialevacuation may occur through each of apertures 104 a, 106 a, 108 a and110 a to create flow cell 112. For example, fluid may be introducedthrough all apertures in chuck body 42, concurrently. Thereafter, fluidmay be evacuated from each of apertures 104 a, 106 a, 108 a and 110 a,one at a time. Before, the concentration in atmosphere 78 of fluidintroduced through apertures 104 a, 106 a, 108 a and 110 a went below adesired level due to evacuation. The fluid may then be reintroducedthrough one or all of apertures 104 a, 106 a, 108 a and 110 a again andthe process repeated to create and/or maintain flow cell 112.

The embodiments of the present invention described above are exemplary.Many changes and modifications may be made to the disclosure recitedabove, while remaining within the scope of the invention. Therefore, thescope of the invention should not be limited by the above description,but instead should be determined with reference to the appended claimsalong with their full scope of equivalents.

1. In an imprint lithography system, a method for reducing gases trappedin viscous liquid positioned on a substrate, said method comprising:providing a substrate having a viscous liquid thereon; placing a moldassembly in close proximity with said viscous liquid, thereby defining aprocessing region proximate to said substrate, said processing regionhaving an atmosphere associated therewith; and varying characteristicsof said atmosphere to increase a transport of gases in said atmosphere,with said transport of said gases being through either said moldassembly, said substrate, or a combination thereof.
 2. The method asrecited in claim 1 wherein varying further includes increasing asolubility of said atmosphere in said substrate, said mold assembly, ora combination thereof.
 3. The method as recited in claim 1 whereinvarying further includes increasing a diffusion of said atmosphere insaid mold assembly, said substrate, or a combination thereof.
 4. Themethod as recited in claim 1 wherein varying further includesintroducing, into said atmosphere, a gas selected from a set of gassesconsisting of carbon dioxide and helium.
 5. The method as recited inclaim 4 further including reducing a pressure of said atmosphere.
 6. Themethod as recited in claim 1 further including forming, from saidviscous liquid, a solidified patterned layer.
 7. In an imprintlithography system, a method for reducing gases trapped in a layer ofviscous liquid positioned on a substrate, said method comprising:placing a mold assembly in close proximity with said substrate, defininga processing region therebetween having an atmosphere associatedtherewith; introducing a fluid into said atmosphere to increase atransport of said gases through either said mold assembly, saidsubstrate, or a combination thereof; and reducing a pressure of saidprocessing region by applying a vacuum to said processing region.
 8. Themethod as recited in claim 7 wherein introducing further includesincreasing a solubility of said atmosphere in said substrate, said moldassembly, or a combination thereof.
 9. The method as recited in claim 7wherein introducing further includes increasing diffusion of saidatmosphere in said substrate, said mold assembly, or a combinationthereof.
 10. In an imprint lithography system, a method for reducinggases trapped in a layer of viscous liquid deposited on a substrate,said method comprising: varying a composition of gases proximate to saidviscous liquid to increase transport of said gases through either saidsubstrate, a mold assembly spaced-apart from said substrate, or acombination thereof.
 11. The method as recited in claim 10 whereinvarying further includes controlling an atmosphere proximate to saidsubstrate by introducing a fluid, therein, saturated with said viscousliquid.
 12. The method as recited in claim 10 further including reducinga pressure of an atmosphere proximate to said substrate.
 13. The methodas recited in claim 10 wherein varying further includes introducing anadditional gas selected from a set of gases consisting of carbon dioxideand helium.
 14. The method as recited in claim 13 wherein additional gasis helium.
 15. The method as recited in claim 10 wherein varying furtherincludes saturating an atmosphere proximate to said viscous liquid witha helium gas.
 16. The method as recited in claim 10 wherein varyingfurther includes introducing into said gases, defining initial gases, anadditional gas having a diffusivity in said mold assembly that isgreater than a diffusivity of said initial gases in said viscous liquid.17. In an imprint lithography system, a method for reducing gasestrapped in an imprint layer formed on a substrate, said methodcomprising: providing a substrate having imprint material depositedthereon; placing a mold assembly in close proximity with said imprintmaterial thereby defining a processing region proximate to saidsubstrate, said processing region having an atmosphere associatedtherewith; introducing helium gas into said atmosphere; and solidifyingthe imprint material to form the imprint layer.
 18. The method asrecited in claim 17 wherein introducing the helium gas further includessaturating said atmosphere with helium gas.
 19. The method of claim 17wherein the imprint layer is patterned.
 20. The method of claim 19further comprising transferring the pattern of the imprint layer intothe substrate.